Risperidone is an atypical antipsychotic drug with benzisoxazole and piperidine functional groups. It acts as a strong dopaminergic antagonist and selective serotonin receptor antagonist. Risperidone is FDA approved for the treatment of schizophrenia since 1993. It is the only drug presently approved for the treatment of schizophrenia in young people under 18 years, and together with lithium, for the treatment of bipolar disorders in children/youth ages between 10-18 years old. Conventional risperidone therapy of schizophrenia involves daily oral tablets, although it is also available as a solution and orally disintegrating tablets.
In fact, one of the intrinsic problems that risperidone-targeted patients usually face is the dissociation (non-compliance) of some schizophrenic patients from the treatment, especially when it therapy consists of a daily dosing, leading to irregular or inconstant treatments and thereby promoting the occurrence of psychotic episodes and crisis. Moreover, this kind of therapy gives rise to high fluctuations in plasma levels (measured as the difference between Cmax and Cmin) in patients, thereby usually affecting the patient's mood.
Risperidone is, therefore, a good drug candidate for incorporation into sustained delivery devices, where the patients would be covered or treated for long time periods with just one dose and without the need of caregivers to pay attention to a daily administration, and where a more homogeneous or level plasma concentration in the patient is desirable.
One of the most usual ways to administer risperidone presently is through the use of depot injections. Depot injections allow careful control of drug usage (as opposed to orally administered drugs) and ensure regular contact between the caregivers team and the patient, where overall treatment efficacy and/or side effects may be identified. Furthermore, it is easy to identify non-compliant patients and prepare interventions. However, in situ forming implants currently described in the state of the art cannot properly control risperidone release from the implant, and fail to allow obtaining therapeutic plasma levels in a bi-weekly administration protocol, with reasonable differences between maximum and minimum concentrations.
Currently, the long-acting injectable risperidone formulation, Risperdal Consta®, is the first depot dosage form with an atypical antipsychotic drug in the market. It is an intramuscular risperidone-containing PLGA microparticle formulation, and it is intended to deliver therapeutic levels of risperidone suitable for bi-weekly administration. However, due to the inherent lag phase of most microparticle based products, the patient is required to supplement the first weeks with daily doses of oral risperidone after first administration. Approximately three weeks after a single intramuscular injection of Risperdal Consta® and concurrent daily doses of oral risperidone, the microspheres release sufficient risperidone in the systemic circulation that the patient can discontinue supplementation with daily doses of the oral therapy. However, this period of oral supplementation presents a risk factor for non-compliance. Also, the presence in the body of two doses at the same time could present a potential risk of adverse events, such as irregular formulation behavior and toxicity (occurrence of unwanted side effects).
The compositions of the invention are based on a biodegradable copolymer poly(L-lactide-co-glycolide) matrix. These polymers have been used for many years in medical applications like sutures described in U.S. Pat. No. 3,636,956 by Schneider, surgical clips and staples described in U.S. Pat. No. 4,523,591 by Kaplan et al., and drug delivery systems described in U.S. Pat. No. 3,773,919 by Boswell et al. However, most of the existing formulations using these biodegradable polymers require manufacturing of an implantable device in solid form prior to the administration into the body, which device is then inserted through an incision or is suspended in a vehicle and then injected. In such instances, the drug is incorporated into the polymer and the mixture is shaped into a certain form such as a cylinder, disc, or fibre for implantation. With such solid implants, the drug delivery system has to be inserted into the body through an incision. These incisions are sometimes larger than desired by the medical profession and occasionally lead to a reluctance of the patients to accepts such an implant or drug delivery system.
U.S. Pat. No. 8,221,778 to Siegel et al. (corresponding to WO 2005/070332) discloses an implant containing risperidone (10-60% wt) and PLGA (90-40% wt) having a lactic acid to glycolic acid ratio of 50:50 to 100:0. These implants are not formed in situ.
Injectable biodegradable polymeric matrix implants based on lactic acid, glycolic acid and/or their copolymers for sustained release have been described in the art. U.S. Pat. No. 5,620,700 issued to Berggren describes a bioerodible oligomer or polymer material containing drug for local application into a diseased tissue pocket such as a periodontal pocket. However, the material requires heating to high temperatures to become sufficiently flowable to allow the injection, so that hardening of the material after cooling to the body temperature forms the implant.
U.S. Pat. No. 6,143,314 to Chandrashekar discloses an injectable composition that forms an implant in situ. The composition is made of drug, organic solvent and a PLGA/PEG block copolymer.
U.S. Pat. No. 6,673,767 issued to Brodbeck describes procedures for in situ formation of biodegradable implants by using biocompatible polymers and biocompatible low water-miscible solvents. A viscous polymeric solution containing the drug that upon injection releases the drug in a controlled manner is obtained through the use of low water-soluble solvents. Solvents with low water-solubility (less than 7% miscibility in water) are used as a way to reduce the release of the drug in aqueous mediums, allowing initial drug releases of 10% or lower during the first 24 hours. However, in our experience, the use of water-immiscible and/or low water-miscible solvents cannot satisfactorily control the initial in vivo release of risperidone during the first 24 hours. For example, the use of benzyl alcohol, a solvent specifically included in U.S. Pat. No. 6,673,767, causes very high plasma levels of risperidone in the first 3 days and then the plasma levels decrease to very low levels in 7 days.
U.S. Pat. No. 6,331,311 issued to Brodbeck also discloses injectable depot compositions comprising a biocompatible polymer such as PLGA, a solvent such as N-methyl-2-pyrrolidone and a beneficial agent such as a drug, further comprising an emulsifying agent such as polyols. However, the compositions disclosed do not perform satisfactorily when the beneficial agent is risperidone, because the use of a two-phase composition with emulsifying agents accelerates implant hydration and increases effective releasing surface area, impairing the control on the initial burst release and causing a fast decrease in drug release from the first days to the following ones. For example, a comparator composition was prepared according to the '311 patent. A container containing risperidone (150 mg), PLGA (300 mg, having an inherent viscosity of 0.32 dl/g and irradiated by β-irradiation to a dose of 25 KGy) and NMP (700 mg) was prepared. Another container containing polyvinyl alcohol in water (1 ml of a 2% w/v). The contents of the containers were mixed, then the mixture was transferred to a syringe and injected intramuscularly (an amount equivalent to 2.5 mg risperidone) into the gluteus of New Zealand White rabbits (n=3). More than 70% of the total AUC of active moiety was released within the first 5 days after the injection. Such a formulation is unable to provide therapeutic plasma levels of risperidone for a period of at least two weeks.
U.S. Pat. No. 4,938,763, issued to Dunn et al., discloses a method for an injectable in situ forming implant. A biodegradable polymer or copolymer dissolved in a water-miscible solvent with a biologically active agent either is dissolved or dispersed within the polymeric solution. Once the polymeric solution is exposed to body fluids, the solvent diffuses and polymer solidifies entrapping the drug within the polymer matrix. Even though Dunn et al. discloses the use of water miscible solvents for obtaining in situ forming polymeric implants, it discloses a number of polymers and solvents and even proportions between the different ingredients that do not produce a satisfactory implant with the appropriate release characteristics, particularly when the implant contains risperidone as active principle. For example, a comparator composition was prepared according to the '763 patent. A container containing risperidone (50 mg) and PLGA (784 mg, monomer ratio of lactic acid to glycolic acid monomer of 75:25, and having an inherent viscosity of 0.20 dl/g was prepared. Another container containing NMP (1666 mg) was prepared. The contents of the containers were mixed. Then the mixture was transferred to a syringe and a portion (1250 mg, corresponding to 25 mg of risperidone) was injected into an aqueous liquid to determine its in vitro release profile. More than 50% of the risperidone was released within the first 2 days. Such a formulation is unable to provide therapeutic plasma levels of risperidone for a period of at least two weeks.
Another way to avoid surgery for administering these drugs is injection of small-sized polymeric particles, microspheres or microparticles containing the respective drug. U.S. Pat. No. 4,389,330 and U.S. Pat. No. 4,530,840 describe a method for the preparation of biodegradable microparticles. U.S. Pat. No. 5,688,801 and U.S. Pat. No. 6,803,055 disclose microencapsulation of 1,2-benzazoles into polymeric particles to achieve a drug release over extended periods of time in the treatment of mental disorders. These microparticles require resuspension into aqueous solvents prior to the injection. These formulations do not form a single (nonparticulate) solid implant.
U.S. Pat. No. 5,770,231 describes a method for producing biodegradable microparticles for sustained release of risperidone and 9-hydroxy-risperidone by dissolving the drug within an organic phase. However, the use of organic solvents that are able to dissolve the risperidone mostly or completely gives rise to very high initial plasma levels of risperidone, after implantation of the particles, due to the diffusion of the drug along with the diffusion of the solvent.
U.S. Pat. No. 7,118,763 describes two methods of making multi-phase sustained-release microparticle formulations based on the combination of different particle sizes or microparticles exhibiting different release profiles. The combination of two different release profiles allows the release of the drug for periods longer than two weeks. However, in practice this combination requires a mixture of particles from at least two different batches, involving the multiplication of end product specifications and increasing batch-to-batch variability.
WO 2008/153611 A2 discloses numerous sustained delivery systems of risperidone and a metabolite. Risperidone is mixed with a soluble thermoplastic polymer, forming an encapsulating residue upon injection from which risperidone is slowly released. However, the authors failed to recognize the influence of process parameters and of specific result effective variables on the initial risperidone burst. In particular, none of the formulations contained a risperidone/polymer mass ratio between 25 and 35%, as in the presently claimed formulations. Moreover, all the tests disclosed therein were carried out using a specific solvent, namely N-methyl-2-pyrrolidone (NMP).
Although microparticle formulations can be administered by injection, they cannot always satisfy the demand for a biodegradable implant because they sometimes present difficulties in the large-scale production. Moreover, in case of any medical complication after injection, they are more problematic to be removed from the body than implantable compositions such as those of the invention.
Therefore, the compositions already described in the state of the art fail to provide suitable extended release risperidone compositions, kits and treatments for psychiatric disorders, and there still exists a need of compositions and devices to allow a controlled, constant release of the drug during prolonged periods of time.